As a result of laboratory experiments in salt water, Sir Humphry Davy reported in 1824 that copper could be successfully protected against corrosion by coupling it to iron or zinc. He recommended cathodic protection of copper-sheathed ships, employing sacrificial blocks of iron attached to the hull in the ratio of iron to copper surface of about 1:100. In practice, the corrosion rate of copper sheathing was appreciably reduced, as Davy had predicted. Later, the British successfully protected the iron work of buoys by attaching zinc blocks and in 1840 produced a zinc alloy particularly suited as a sacrificial anode. When wooden hulls were replaced by steel, the fitting of zinc slabs became traditional on all Admiralty vessels. These slabs provided localized protection, especially against the galvanic effects of the bronze propeller.
Brass and bronze hardware on marine propeller assemblies have been provided with a variety of protective devices in the prior art to reduce their electrochemical and galvanic corrosion in sea water. Typically these prior art devices include threaded surfaces in zinc or brass materials which screw onto the propeller shaft proximate to the propeller to be protected. These structures are expensive to manufacture and, since their anodic portions are intentionally designed for sacrificial corrosion, they are even more expensive to use and replace.